Our goal of understanding crystallin gene expression during development and disease has been advanced as follows. More evidence has been obtained that electrolyte imbalances may alter crystallin metabolism in cataracts. Differential reduction in beta- and gamma-crystallin synthesis and crystallin degradation have been found in a new hereditary mouse cataract (Philly mouse) associated with ion changes. Na ion, K ion, Cl negative, and OAc negative were shown to effect the ratio of synthesis of the delta-crystallin polypeptides in a reticulocyte lysate as well as in the cultured chick lens treated with ouabain, providing direct evidence that electrolytes may alter crystallin synthesis. Experiments have indicated that the ion-related changes in delta-crystallin synthesis may involve a partial cleavage of the larger polypeptides associated with translation or a direct effect of ions on initiation or termination of translation. We have correlated subunit composition with isoelectric points of delta-crystallin, providing a basis for the charge heterogeneity of the protein. Delta-crystallin gene sequences have been cloned; 16 intervening sequences have been detected in the delta-crystallin genomic fragments. Finally, chicken beta-crystallins have been purified and their polypeptide composition studied with respect to size and tryptic peptides.